Petri dish



Feb. 14, 1961 T. J. cARsKl PETRI DISH Filed June 16. 1958 1li 2 m c ,m lMULTI* BY j ATTORNEYS United States Patent O PETRI DISH Theodore J.Carski, Baltimore, Md., assigner to Baltimore Biological Laboratory,Inc., Baltimore, Md., a corporation of Maryland Filed June 16, 1958,Ser. No. 742,357 2 Claims. (Cl. 195-139) This invention relates to astructurally and functionally improved Petri dish.

By means of the present teachings an assembly is furnished in whichevaporation is prevented. Also, it may be transported without disturbingthe seal established by its components or the material contained withinthe dish.

The parts of the dish assembly, when applied one to the other, willassure the establishment of an adequate seal. The dish may accommodateconstant-humidity preparations or material which will absorb gases.Reactive agents useful in this connection may be maintained insegregated condition until the user, by suitable manipulation of theassembly, intermixes those agents.

A Petri dish assembly as herein disclosed may wfth propriety be disposedof after a single use. The parts thereof can be readily and economicallymanufactured; the dish being capable of proper use even by personshaving in effect no mechanical aptitude.

With these and other objects in mind, reference is had v to the attachedsheet of drawings illustrating one practical embodiment of the inventionand in which:

Fig. 1 is a perspective View of the components providing the Petri dishassembly and illustrating them in separation condition;

Fig. 2 is a sectional side view of the complete assembly;

Fig. 3 is a fragmentary transverse sectional view in enlarged scale of adetail of the parts as illustrated in Fig. 2;

Fig. 4 is a bottom plan view of the cover unit;

Fig. 5 is a top plan view of the dish or receptacle unit;

Fig. 6 is a fragmentary sectional view taken along the line 6 6 in thedirection of the arrows as indicated in Fig. 7; and

Fig. 7 is a sectional and elevational view taken along the line 7-7 inthe direction of the arrows as indicated in Fig 6 Referring primarily toFigs. l, 3 and 4 and with particular reference to the cover unit of theassembly, it will be seen that its body 10 includes a preferably datsection from the edge of which a skirt or liauge 11 depends. The edge ofthis flange, as indicated at 12, is preferably inclined in an outwardlyand downwardly extending direction. The inner surface of the coveradjacent the zone of juncture of skirt 11 and body 10 is thickened toembody therein maximum rigidity. The surface of this Zone, as indicatedat 15, provides an upwardly and inwardly extending guiding face. Agroove 13 is furnished adjacent the inner edge of face 15 and extendsthroughout the entire circumference of the cover. Preferably this groovefurnishes, at points spaced 120 apart, recesses 14.

The body of the dish includes a base 16 formed with a first annular wall17 at a point spaced from its side edge. A second wall 18 is providedpreferably in line with lthat edge. The face of base 16 may be furnished2,971,892 Patented Feb. 14, 1961 with indicia 19 of any desiredcharacter providing counting chart or grid markings in accordance withconventional techniques. Both the cover and the base of the assembly areconveniently formed of polystyrene, and the indicia may be appliedthereto by screen marking.

As illustrated especially in Figs. 2 and 3, wall 17 is convenientlytapered and terminates in a rounded edge portion 19" having a radiussubstantially equal to that of groove 13. Wall 18 may be of constantthickness and terminates in an edge mating with edge 12. The parts areso proportioned in height that when the edges of ange or skirt 11 andwall 18 are in engagement, the rounded edge portion 19 of wall 17 bearsagainst the base of groove 13. Preferably the outer faces of the skirt11 and wall 18 are at and in line, so that a pressure-sealing tape 20may be applied thereto, as indicated in dot-and-dash lines, to preventaccidental separation of the cover from the base of the dish.

Extending upwardly from the edge 19' of wall 17 are projections 21.These are spaced 120 apart and are of an area such that they may bereceived within the recesses or depressions 14 in the base of the covergroove 13. intervening walls 17 and 18 is a trough portion 22. Thistrough portion is subdivided by ribs 23 extending upwardly from itsbase, conveniently at diametrically opposite points, as illustrated. Theheight of these ribs may conveniently be less than the depth of thetrough portion 22.

With a Petri dish assembly of this type it will be understood Ithat adisposable structure is provided. The parts should be designed so thatthey will remain rigid, with no distortion of shape, in a temperaturerange between the high and low points encountered in techniques involving their use. After manufacture of the parts, `they will besterilized and may be lled with culture medium and sealed with tape, asindicated at 20, or in any other suitable manner. Of course, prior tosuch sealing, the edge portfons of either or both of walls 17 and 18will have applied to them a light coating of a material such asVaseline. Therefore, with the cover applied to the bottom, an adequateseal is furnished to prevent evaporation.

Obviously, the dish assembly may be incubated employing this or asimilar seal. Also, an air lock is thus provided between walls 17 and18. Thus, all air currents are prevented from moving inwardly oroutwardly of this space. Also, foreign material such as dust will notenter if the assembly is incubated in an inverted position. In theapplication of the cover to the bottom plate, the parts will beself-centered. This will be due to the guiding surface 15 cooperatingwith the rounded upper edge 19 of wall 17. Moreover, the adjacent edgesurfaces of ange 11 and wall 18 will cooperate as the parts are appliedto each other.

The trough 22 may be used to accommodate constanthumidity preparations.These would involve, for example, sulfuric acid solutions of selecteddensity resulting in the following factors:

Density l.50=7().4% relative humidity Density 1.50=18.8% relativehumidity Likewise, various salts may be used to produce an atmosphere ofconstant humidity, including calcium chloride and ammonium chloride.Functionally equivalent substances and agents could likewise beemployed.

In the event it is desired to absorb gases, the well or trough portionmay be employed to remove oxygen from the entrapped air by means ofpyrogallo and sodium hydroxide. To effectively obtain this result, thedividing Walls or ribs 23 should-as shown-be of less height than thedepth of the trough or well. This will permit separation of the activeagents, which are mixed subse` quently to the application of the coverto the bottom plate, and with the Vaseline or equivalent seal appliedonly to the adjacent opposed surfaces of ange 11 and Wall 18. Likewise,carbonates and acids could b e disposed in the segregated areas of thewell or trough portiony and subsequently mixed, to produce suitableconcentrations of carbon dioxide to promote the growth of certainmicroorganisms.

Thus, among others, the several objects of the invention as specificallyaforenofted are achieved. Obviously, numerous changes in constructionand rearrangements of the parts might be resorted to without departingfrom the spirit of the invention as defined by the claims.

I claim:

1. A Petri dish assembly including in combination a body comprising abase, a pair of walls of limited height extending upwardly from saidbase, said walls being disposed-one within and spaced from the other tofurnish a trough portion between them, the inner wall having a heightgreater than that of the outer Wall and together with said base,defining a shallow receptacle, a cover, a skirt depending therefrom,said cover providing adjacent said skirt an inwardly and upwardlyinclined surface engaging with the edge of the inner wall to guide theskirt into sealing engagement with the edge of the outer Wall as saidcover is applied to said base, said cover being formed with a groove inits face, said groove being spaced from said skirt a distance equal tothe spacing of said walls from each other to cause said groove toreceive the edge zone of the inner wall as said cover is applied to saidbase, the surface of said groove and the edge zone of said inner wallbeing both transversely rounded, said groove being formed with recessedportions, and projections extending upwardly of said inner wall intosaid recessed portions.

2. A Petri dish assembly including in combination a 'body comprising abase, a pair of walls of limited height extending upwardly from saidbase, said walls being disposed one within and spaced from the other tofurnish a trough portion between them and with the inner wall defining ashallow receptacle, a cover body, a skirt de pending therefrom, saidcover being disposed above said base and being formed with a groovereceiving the edge zone of'said innerY Wall as Said skirt sealinglyengages said outer wall, said groove being formed with recessedportions, and projections extending outwardly from said inner wall intosaid recessed portions.

References Cited in the le of this patent UNITED STATES PATENTS1,083,104 Johnson Dee. 3o, 191s 1,732,996 Wandel Oct. 22, 1929 2,348,448Brewer May 9, 1944 y2,677,647 Lovell May 4, 1954 FOREIGN PATENTS 387,795Great Britain Feb. 16, 1933

2. A PETRI DISH ASSEMBLY INCLUDING IN COMBINATION A BODY COMPRISING A BASE, A PAIR OF WALLS OF LIMITED HEIGHT EXTENDING UPWARDLY FROM SAID BASE, SAID WALLS BEING DISPOSED ONE WITHIN AND SPACED FROM THE OTHER TO FURNISH A TROUGH PORTION BETWEEN THEM AND WITH THE INNER WALL DEFINING A SHALLOW RECEPTACLE, A COVER BODY, A SKIRT DEPENDING THEREFROM, SAID COVER BEING DISPOSED ABOVE SAID BASE AND BEING FORMED WITH A GROOVE RECEIVING THE EDGE ZONE OF SAID INNER WALL AS SAID SKIRT SEALINGLY ENGAGES SAID OUTER WALL, SAID GROOVE BEING FORMED WITH RECESSED PORTIONS, AND PROJECTIONS EXTENDING OUTWARDLY FROM SAID INNER WALL INTO SAID RECESSED PORTIONS. 